Road Runner Nest

Hi Everyone,I am having a problem when i step on the gas hard.It back fires ,sputters and may stall.This is with a rebuilt avs #4968S .I put another rebuilt avs on tonight and it seams to be the same.Car runs fine otherwise just the stumble at hard take off.I have a new correct fuel pump and a new mopar Dist.
The engine is 1976 or 77 "440" W/small spark plugs.I have no idea if it was rebuilt or Horsepower.Car was raced before i got it.Any thoughts on timing # or spark plug # Thanks,, Gary '71' GTX Goldleaf met.

back off the timing
Take you're air and idle mixture screw and put them all the way in, Then bring them out one and a half turns each. Try that.

If you're sure timing is close to being ok. If not, start off with about 10 degrees before TDC, with vacuum advance disconnected, and plugged at the carb.
After you check/set timing, disconnect the secondary link on the side of the carb. This will let you test the primary side and accelerator pump. Hook the vacuum advance back up, and test drive.
Let us know if anything changes!